A couple of things up front: I'm no audiophile and I'm new to building my own speakers. With those caveats in mind, can someone answer a question that's been bugging me since I started researching DIY speaker building: why is everyone striving for flat freqquency responses, since that isn't how our hearing works?

My wonder got quite a boost last night. I was invited to hear a very expensive, highly tuned system. There were enough Sunfire amps in the room to power a large cruiseliner. The owner had built the speakers himself out of the finest components he could find. Then he spent days and days tweaking them until his response curve was remarkably flat. He even took them to a recording studio in town for testing. I was impressed with his data. Then he played them for me. They were about the worst sounding speakers I've ever heard. Harsh and shrill to an extreme. In fact, they had a treble boost that I feared was going to peel the paint from the walls, if it didn't burn the skin from my body first. I'm glad the guy liked them, but I thought they were hideous.

So I'm asking, do people really like that sound? We don't have flat hearing curves, and it seems odd to me that we would want our speakers to emit sounds that are artifically boosted. It has been a long, long time since I fooled with any audio gear, but back in the early `70s when I was first interested in sound systems, the idea was to match your speakers' response with your hearing. Can't remember the specs exactly, but that required a pretty significant dip in the midrange, as much as 8-10 db at high SPLs.

So what's the deal? After a lifetime of open exhaust race cars and rock 'n roll, I know it's not because I have good high freq hearing.

I think the emphasis will make more sense if you start by recognizing this fact:

What our speakers reproduce and what we hear are two different things.

So, it's important for speaker frequency response to be flat because we want our speakers to reproduce sound exactly the way it was originally produced. That doesn't have anything to do with how sensitive our ears are to certain frequencies, or whether we having high frequency hearing damage.

Think of it this way, if you were to attend a music event live and that same event was also being recorded. You would listen during the event and the sound you are precieving and the sound that is actually occuring is different because, as you stated, our ears do not have a flat frequency response. But the sound that is occuring and the sound that is recorded will be very similar, and this is important. When our speakers reproduce that sound we want them to accurately reproduce what was recorded (and therefore accurately reproduce the sound the actually occured) so that we can precieve the sound the same way as when we heard it live.

I hope this helps clear things up, but if not, just know this. The fact that our ears do not have flat frequency response does not rid use of the need for speakers that have flat frequency response.

Without arguing over whether 'flat response' (what do you mean by this, flat response on axis, off axis, flat power response?) is desireable or not, have a look at the articles below to understand why many promote a flat power response:

Basically as far as I can tell, the focus on flat power response (NOT the same as most people's conception of 'flat response') is all traceable back to Floyd Toole's excellent research at the NRC in Canada.

You are assuming that "harsh sound" is a result of "flat response" when in fact the quality of his speakers or lack thereof may be stemming from a totally different issue. I bet you could take a very nice, expensive, flat ribbon tweeter and cross it too low and it will happily peel the paint from your walls.

It sound like your friend needs to treat his room. Even the best speakers will sound bad in a bad room. Also, for measurements to be truly valid they need to be done at the seating position in the room they are used.

The idea of flat response is that it is necessary to perfectly reproduce what is on the recording, which is a valid point. However, just because it's flat doesn't necessarily mean that it sounds good. It just means that any frequency is played with equal SPL. That doesn't mean that flat response equals bad sound. Yes, our ears have different sensitivities to different frequencies, but that doesn't have anything to do with whether or not a speaker's FR should be flat. A flat FR is a perfectionist's goal in designing and building speakers.

Any dipole fan like myself will say that flat response is overrated because with dipoles a flat response is impossible, yet when done right they sound great, at least to us.

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So, it's important for speaker frequency response to be flat because we want our speakers to reproduce sound exactly the way it was originally produced. That doesn't have anything to do with how sensitive our ears are to certain frequencies, or whether we having high frequency hearing damage.

Thanks for your gentlemanly response. But you're wrong. I looked at the results of his in-room testing, after the room had been tweaked. Flat as a pancake. So, something was up: the test equipment might not have been properly calibrated, or maybe my ears are out of whack. Whatever the reason, I couldn't live with his speakers for more than a few seconds.

If you design for flat on axis response and disregard all else, I'm sure your system will sound quite bad.

Quote:

maybe my ears are out of whack

If as you say you've sustained some hearing damage over the years, your high frequency hearing would likely be serverly compromised. Which is what makes it so puzzling to me that you heard a 'treble boost', which as Bill rather bluntly pointed out, is impossible in a 'flat' (btw, you still haven't defined this in the context of your friends stereo) system. Maybe the treble sounds shrill, harsh, or just plain wrong, but if the system measures flat, there is by definition no 'treble boost', at least not on the measurement axis.